JP7230747B2 - Ferrite core and wire wound coil components - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ferrite core that provides a core portion on which windings are arranged in a wire-wound coil component, for example, and a wire-wound coil component provided with the ferrite core. The present invention relates to improvements for improving mechanical strength and magnetic permeability.

For example, in Japanese Patent Application Laid-Open No. 2017-204595 (Patent Document 1), a winding core portion (axial core portion) extending in the length direction and provided at both ends in the length direction of the winding core portion and orthogonal to the length direction and a collar portion projecting from the winding core portion in a height direction and a width direction orthogonal to both the length direction and the height direction.

In the technique described in Patent Document 1, attention is paid to the difference between the existence ratio of pores in the core portion and the existence ratio of pores in the collar portion, not the ratio of pores in the ceramic core itself. Generally, the ratio of pores in the collar is larger than the ratio of pores in the winding core, and this difference is preferably within 20%, more preferably within 15%, and most preferably within 10%. It is said to be within

In paragraph 0044 of Patent Document 1, it is described that, as described above, by bringing the existence ratio of pores in the flange closer to the ratio of pores in the winding core, it is possible to suppress a decrease in strength in the flange. ing.

JP 2017-204595 A

As described above, Patent Document 1 focuses only on the difference between the ratio of pores in the winding core and the ratio of pores in the flange, and the ratio of pores in the ceramic core (hereinafter referred to as "pore ratio") There is no specific value specified for itself. However, the inventors of the present invention recognize from their experience that the porosity of the ceramic core usually does not fall below 2.0%.

In a ceramic core, the higher the porosity, the lower the mechanical strength. For example, in a ceramic core whose length dimension is 4.5 mm and width dimension is 3.2 mm, and whose dimensions are less than 5.0 mm, a porosity of 2.0% or more will improve the mechanical strength. It was found that the degree of freedom in designing the core shape was restricted. In particular, from the viewpoint of miniaturization and maintenance of characteristics, ferrite cores are being miniaturized, but the diameter of the wire wound around the ferrite core does not change. If it is attempted to be wound around the winding core without protruding further, the winding core will be thinner than the collar, and there is a risk that such miniaturization will be limited. In order to reduce the porosity, it is conceivable to increase the pressure applied during molding of the ceramic core. It is also difficult to increase the pressure.

As described above, the current situation is that it is very difficult to make the porosity of the ceramic core less than 2.0%.

Furthermore, when the ceramic core is made of a magnetic material such as ferrite, a high porosity results in a decrease in magnetic permeability, resulting in a problem of deterioration in the characteristics of a coil component using the ceramic core.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a ceramic core made of ferrite capable of achieving high mechanical strength and high magnetic permeability, that is, a ferrite core, and a wire-wound coil component comprising the ferrite core.

A ferrite core according to the present invention includes a winding core portion extending in a length direction, and flange portions provided at both ends in the length direction of the winding core portion and protruding from the winding core portion in a height direction perpendicular to the length direction. , is composed of the ferrite sintered body itself , which is a sintered body of a pressure-molded body of ferrite powder integrally formed. It is 0.3 times or more and 0.6 times or less, and pores are present inside the core portion and the collar portion.

In order to solve the above-mentioned technical problems in such a ferrite core, in the present invention, the existence ratio of pores in the winding core is 0.05% or more and 1.00% or less, and the number of pores in the flange is The presence ratio is characterized by being 0.05% or more and 1.20% or less .

A wire-wound coil component according to the present invention is characterized by comprising the above-described ferrite core and windings disposed on a winding core.

ADVANTAGE OF THE INVENTION According to this invention, the ferrite core which can implement|achieve high mechanical strength and high magnetic permeability, and the wound coil component provided with the said ferrite core can be obtained.

1 is a front view showing a coil component 10 having a ferrite core 20 according to a first embodiment of the invention; FIG. 2 is a perspective view showing alone a ferrite core 20 included in the coil component 10 shown in FIG. 1. FIG. FIG. 3 is a schematic cross-sectional view showing a powder molding device 60 for obtaining the ferrite core 20 shown in FIG. 2; 4 is a plan view showing a die 61 provided in the powder molding apparatus 60 shown in FIG. 3. FIG. FIG. 4 is a schematic cross-sectional view showing a stage in which molding of a molded body 20A for the ferrite core 20 is completed by the powder molding apparatus 60 shown in FIG. 3; FIG. 4 is a front view showing a ferrite core 21 according to a second embodiment of the invention; FIG. 11 is a perspective view showing a portion of a ferrite core 22 according to a third embodiment of the invention; It is a diagram showing a SEM photographed image of a cross section of a ferrite sintered body, (A) shows a cross section of a ferrite sintered body with a porosity of 0.1%, and (B) shows a ferrite sintered body with a porosity of 0.4%. (C) shows a cross section of a ferrite sintered body with a porosity of 2.4%, and (D) shows a cross section of a ferrite sintered body with a porosity of 3.0%.

[First Embodiment]
As shown in FIG. 1 , the wire wound coil component 10 has a ferrite core 20 , terminal electrodes 50 and windings 55 . The ferrite core 20 is made of a ferrite sintered body in which a winding core portion 30 and a pair of flange portions 40 provided at both ends of the winding core portion 30 are integrally formed. Thus, since the ferrite sintered body itself is the ferrite core 20, in the following description, the reference numeral "20" used to refer to the ferrite core will also be used to refer to the ferrite sintered body. .

Here, for example, as shown in FIGS. 1 and 2, the direction in which the pair of flanges 40 are arranged is defined as the “length direction Ld”, and the direction perpendicular to the “length direction Ld” shown in FIGS. 2, that is, the direction perpendicular to the formation direction of the terminal electrodes 50 (main surface direction of the mounting substrate) is defined as the “height direction Td”, and the “length direction Ld” and the “height direction Td” A direction orthogonal to both and parallel to the formation direction of the terminal electrodes 50 (the principal surface direction of the mounting substrate) is defined as a “width direction Wd”.

The core portion 30 has a quadrangular prism shape extending in the length direction Ld. The central axis of the winding core 30 extends parallel or substantially parallel to the length direction Ld. The winding core portion 30 has an upper surface 31 and a lower surface 32 extending in opposite directions and parallel to each other in the height direction Td, and a pair of side surfaces 33 and 34 extending in opposite directions and parallel to each other in the width direction Wd. have.

Note that the “quadrangular prism shape” includes a quadrangular prism with chamfered corners and edges and a quadrangular prism with rounded corners and edges. In addition, unevenness or the like may be formed on part or all of the upper surface 31 , the lower surface 32 and the side surfaces 33 and 34 .

A pair of flanges 40 are provided at both ends of the winding core 30 in the length direction Ld. Each flange 40 has a rectangular parallelepiped shape with a relatively short length measured in the length direction Ld. Each collar portion 40 is formed to protrude from the winding core portion 30 in the height direction Td and the width direction Wd.

Note that the flange portion 40 does not need to protrude from the winding core portion 30 only in the height direction Td and not in the width direction Wd. That is, the side surfaces 43 and 44 of the collar portion may be positioned on the same plane as the side surfaces 33 and 34 of the winding core portion 30 . However, as described above, if each flange portion 40 is formed to protrude from the winding core portion 30 in the height direction Td and the width direction Wd, the ferrite core 20 will have a more complicated shape and will be damaged more. Therefore, the effect of improving the mechanical strength becomes more significant.

Each flange 40 has a pair of end surfaces 41 and 42 extending parallel and opposite to each other in the length direction Ld, and a pair of side surfaces 43 extending parallel and opposite to each other in the width direction Wd. 44, and an upper surface 45 and a lower surface 46 extending in opposite directions and parallel to each other in the height direction Td. An end portion of the winding core portion 30 is positioned on the one end surface 41 described above. The end surface 41 of each collar portion 40 faces inward and is arranged in parallel with and opposite to the end surface 41 of the other collar portion 40 . The other end face 42 faces outward.

Terminal electrodes 50 are provided on the lower surface 46 described above, as shown in FIG. Terminal electrodes 50 are electrically connected to conductive lands of a circuit board, for example, when coil component 10 is mounted on a mounting board. At this time, since the length direction of the winding core portion 30 is parallel to the mounting substrate, the wire-wound coil component 10 with a high Q value can be configured.

The winding 55 is wound around the core 30 as shown in FIG. The winding 55 has a structure in which a core wire containing, for example, a conductive metal such as Cu or Ag as a conductive component is covered with an electrically insulating material such as polyurethane or polyester. The diameter of winding 55 is, for example, about 20 μm. Both ends of the winding 55 are electrically connected to the terminal electrodes 50 respectively.

In order to manufacture such ferrite core 20 and coil component 10 including ferrite core 20, for example, the following steps are performed.

First, ferrite powder is prepared, and the ferrite powder is pressure-molded to produce a compact containing the ferrite powder. In this molding process, for example, a powder molding device 60 as shown in FIGS. 3 to 5 is used. Note that the powder molding device 60 is described in detail in the above-mentioned Patent Document 1.

As shown in FIG. 3, the powder molding apparatus 60 has a die 61, a lower punch assembly 70, an upper punch assembly 80 and a feeder 90. As shown in FIG.

The die 61 is formed with a cavity 62 penetrating in the height direction Td. As shown in FIG. 4, the opening of the cavity 62 has substantially the same H shape as the planar shape of the ferrite core 20 shown in FIG. 2 when viewed from the height direction Td. That is, the cavity 62 has a pair of first cavity portions 62A corresponding to the pair of collar portions 40 shown in FIG. 2, and a second cavity portion 62B corresponding to the winding core portion 30. At this time, in the cavity 62, the width dimension w1 measured in the width direction Wd of the second cavity portion 62B is, for example, 0.3 times or more and 0.3 times the width dimension W1 measured in the width direction Wd of the first cavity portion 62A. It is set to be 6 times or less.

As shown in FIG. 3, the lower punch assembly 70 has a structure divided into a first lower punch 71 for forming the collar portion and a second lower punch 72 for forming the core portion. The first lower punch 71 and the second lower punch 72 are lowered and raised by a first drive source 73 and a second drive source 74, respectively. Therefore, the first lower punch 71 and the second lower punch 72 can be lowered and raised independently of each other.

The upper punch assembly 80 has a structure divided into a first upper punch 81 for forming the collar portion and a second upper punch 82 for forming the core portion. The first upper punch 81 and the second upper punch 82 are lowered and raised by a first drive source 83 and a second drive source 84, respectively. Therefore, the first upper punch 81 and the second upper punch 82 can be lowered and raised independently of each other. As the drive sources 73, 74, 83 and 84, for example, servo motors can be used.

A feeder 90 for storing the ferrite powder 95 and supplying it to the cavity 62 has a box shape. The feeder 90 is provided so as to be movable in the horizontal direction (longitudinal direction Ld) in FIG. 3 while being in contact with the upper surface of the die 61 .

The powder molding apparatus 60 is a multi-axis press type (multistage press type) powder molding apparatus. For example, while the die 61 is fixed, the punches 71, 72, 81 and 82 are independently driven. The powder molding device 60 performs the following steps.

First, the feeder 90 is moved above the cavity 62 and the ferrite powder 95 is supplied into the cavity 62 from the opening of the feeder 90 while the lower punch assembly 70 is lowered with respect to the die 61 by a predetermined amount. This causes the cavities 62 to be filled with ferrite powder 95 in excess of the final desired filling amount.

Subsequently, the lower punch assembly 70 is raised relative to the die 61 to push excess ferrite powder 95 back into the feeder 90 to tightly pack the ferrite powder 95 into the cavity 62 .

Feeder 90 is then returned to the position shown in FIG. At this time, the side walls of the feeder 90 and the like scrape off the ferrite powder 95 protruding from the cavity 62 .

The upper punch assembly 80 is then moved downwardly into the cavity 62 . At this time, before the upper punch assembly 80 enters the cavity 62, the lower punch assembly 70 is moved downward with respect to the die 61 to the position shown in FIG. be.

Next, as shown in FIG. 5, the closed space surrounded by the lower punch assembly 70, the upper punch assembly 80, and the die 61 is filled with the ferrite powder 95, and the first and second lower punches 71, 72 and the first and the second upper punches 81, 82 are moved closer to each other, pressure is applied by the lower punch assembly 70 and the upper punch assembly 80, and the molded body 20A is molded.

At this time, since each of the punches 71, 72, 81, 82 can be independently driven in the powder molding apparatus 60, the amount of movement of each of the punches 71, 72, 81, 82 with respect to the die 61 can be individually controlled. can be controlled to As a result, it is possible to freely adjust the pressure applied to each of the core portion 30 and the collar portion 40 in the molded body 20A, that is, the degree of compression.

Therefore, by controlling the amount of movement of each of the punches 71, 72, 81, 82, the ratio of the dimension t1 along the pressurizing direction of the core 30 to the dimension T1 along the pressurizing direction of the collar 40 It is easy to adjust t1/T1 so that 0.3≤t1/T1≤0.6, for example. Also, by controlling the amount of movement of each of the punches 71, 72, 81, 82, it is easy to make the degree of compression at the collar portion 40 and the degree of compression at the winding core portion 30 equal to each other. .

After that, the lower punch assembly 70 and the upper punch assembly 80 are moved upward with respect to the die 61 so that the compact 20A is carried out of the die 61 . Then, the molded body 20A is taken out by separating the lower punch assembly 70 and the upper punch assembly 80 from each other.

Next, the compact 20A is fired in a firing furnace. By this firing, the ferrite sintered body 20 is obtained. Subsequently, the ferrite sintered body 20 is put into the barrel and polished with an abrasive. By this barrel polishing, burrs are removed from the ferrite sintered body 20, and the outer surface of the ferrite sintered body 20 (especially corners and ridges) is rounded.

Subsequently, the terminal electrode 50 is formed on the lower surface 46 of the flange portion 40 of the ferrite core 20 made of the ferrite sintered body. For example, a conductive paste containing Ag or the like as a conductive component is applied to the lower surface 46 of the collar portion 40, and then baked to form a base metal layer. Thereafter, a nickel (Ni) plating film and a tin (Sn) plating film are sequentially formed on the base metal layer by electroplating, thereby forming the terminal electrode 50 . In addition, the terminal electrode 50 may be configured to include one obtained by processing a metal plate.

Next, the winding 55 is wound around the winding core portion 30 of the ferrite core 20, and the end of the winding 55 is joined to the terminal electrode 50 by a known method such as thermocompression bonding. Thus, the coil component 1 is completed.

The ferrite sintered body 20 is, for example, Ni—Cu—Zn based ferrite, Ni—Zn based ferrite, Cu—Zn—Mg based ferrite, Cu—Zn based ferrite, Mn—Mg—Zn based ferrite, Mn—Zn based ferrite. etc., depending on the properties required.

Pores are present inside the ferrite core 20 made of a sintered ferrite body, that is, inside each of the core portion 30 and the flange portion 40 . The present invention is characterized in that the core portion 30 has a porosity of 0.05% or more and 1.00% or less. The porosity was obtained as follows.

Using an ion milling device (Hitachi High-Technologies Corporation: IM4000), the ferrite core 20 to be evaluated was polished to expose the cross section of the substantially central portion of the winding core portion 30, which is the evaluation portion. Subsequently, using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation: S-4800), the exposed cross section was imaged using a secondary electron beam at an acceleration voltage of 1 kV, a measurement time of 20 seconds, and a magnification of 1000 times. Under the condition of 1260×880 pixels, six images were taken in a range of 95 μm×126 μm per field of view. Next, using image analysis software (manufactured by Asahi Kasei Engineering Co., Ltd.: Azo-kun), particles are extracted from the pores in the photographed image, and this is binarized to obtain the total area of the pores. Pore area ratio was calculated. This pore area ratio was taken as the pore ratio.

Note that the binarization process was specifically performed as follows. First, the gradation (light intensity) of each pixel in the photographed image is calculated as a rational number, and the rational number is converted into 256 levels (8 bits) from 0 (dark) to 255 (light), and the gradation is converted into value. Next, the grayscale value and its frequency (the number of pixels) of each image are shown in a histogram. At this time, an image whose density value D50 is not 75-125 is rejected as an analysis image. Furthermore, the grayscale value "D90-D10" of the image is set as the grayscale value spread value, and the image whose spread value is not 20-35 is also rejected as the analysis image. If it is not possible to capture six or more images with a density value D50 of 75-125 and a spread value of 20-35, the shooting conditions are reviewed.

For the analysis image selected as described above, in the above-mentioned histogram, an accumulated curve is calculated from the density value 0 of the frequency (number of pixels), and the first approximate straight line and the second approximate straight line are calculated as follows for the accumulated curve. pull like

First approximation straight line: A straight line connecting a point corresponding to D30 and a point corresponding to D40 on the accumulated curve.

Second approximation line: A point on the accumulated curve corresponding to the gray value obtained by subtracting -30 from the point corresponding to D10 on the accumulated curve, and a gray value obtained by subtracting -40 from the point corresponding to D10 on the accumulated curve. A straight line connecting the corresponding points on the stacked curve.

Then, the gradation value at the point where the bisector of the first approximate straight line and the second approximate straight line and the accumulated curve intersect is set as the threshold value for the binarization process. That is, pixels with grayscale values equal to or lower than the threshold value are determined to be pores, and the pore area ratio is calculated based on the number of pixels, and this is taken as the pore ratio.

When the porosity is 1.00% or less, it is possible to achieve both freedom in designing the shape of the ferrite core and mechanical strength. Even if the content is 0.50% or less, severe reliability test conditions can be satisfied. Therefore, the porosity of the winding core 30 is set to 1.00 % or less as described above, but it is further reduced, preferably 0.70% or less, and most preferably 0.50%. % or less.

FIG. 8 shows cross-sectional SEM images of several actually manufactured ferrite sintered bodies. When the ferrite sintered bodies shown in FIGS. 8A to 8D were produced and the porosity of each was measured, the ferrite sintered body of (A) had a porosity of 0.1%, and (B) The ferrite sintered body of has a porosity of 0.4%, the ferrite sintered body of (C) has a porosity of 2.4%, and the ferrite sintered body of (D) has a porosity of 3.0%. rice field. In FIGS. 8A to 8D, black spots are pores.

As can be seen by comparing between FIGS. 8 (A) to (D), the pores are the largest and most abundant in (D), and in the order of (D), (C), (B), and (A), Smaller and fewer, being smallest and least in (A).

In addition, when the 3-point bending strength was measured for a plate-shaped ferrite sintered body of length 7.0 mm × width 27.5 mm × thickness 1 mm, the ferrite sintered body with a porosity of 2.5% or more and equivalent to the conventional product Compared to the body
(1) A ferrite sintered body with a porosity of more than 0.70% and less than or equal to 1.00% was confirmed to have a strength improvement of 15%,
(2) A ferrite sintered body with a porosity of more than 0.50% and less than or equal to 0.70% was confirmed to have a strength improvement of 39%,
(3) A ferrite sintered body with a porosity of more than 0.05% and less than or equal to 0.50% was confirmed to have improved strength by 82%.

In the case of ferrite sintered bodies having a porosity of 0.05% or less, no strength improvement effect exceeding the above case (3) was confirmed. It is presumed that this is because the fracture starting point changed from the internal pore of the ferrite sintered body to the surface pore. Therefore, it is not necessary to set the porosity to 0.05% or less, and it can be said that a value exceeding 0.05% is sufficient.

In order to improve the strength of the ferrite core 20, it is preferable to improve the strength not only of the winding core portion 30 but also of the flange portion 40. FIG. Compared to the core part 30, the porosity of the collar part 40 is difficult to reduce in terms of powder molding. A higher setting is practically preferable. Therefore, it is preferable that the porosity of the flange portion 40 is higher than that of the winding core portion 30 by about 0.20%. More specifically, the porosity of the flange 40 is preferably 0.05% or more and 1.20% or less, more preferably 0.84% or less, and 0.60% or less. is most preferred.

The measurement of the porosity of the collar portion 40 can be performed in the same manner as the measurement of the porosity of the winding core portion 30 described above, except that the cross section of the substantially central portion of the collar portion 40 is used as the evaluation point.

In order to obtain the ferrite sintered body 20, the porosity as described above, more specifically, the porosity as shown in FIGS. When the profile was adopted, it was confirmed that it could be realized.

(1) When a firing profile is adopted in which the temperature is increased from 600°C to 1200°C over 25 hours and then decreased to 600°C over 25 hours, the porosity of the winding core 30 is 0.05% or more and 1.00% or less, and the porosity of the flange portion 40 was 0.05% or more and 1.20% or less.

(2) When adopting a firing profile in which the temperature is increased from 600°C to 1200°C over 80 hours and then decreased to 600°C over 80 hours, the core portion 30 has a porosity of 0.05% or more and 0.70% or less, and the porosity of the flange portion 40 was 0.05% or more and 0.84% or less.

(3) When adopting a firing profile in which the temperature is increased from 600°C to 1200°C over 210 hours and then decreased to 600°C over 210 hours, the core portion 30 has a porosity of 0.05% or more and 0.50% or less, and the porosity of the flange portion 40 was 0.05% or more and 0.60% or less.

In this way, if the process of raising the temperature from 600° C. to 1200° C. takes a very long time such as 25 hours, 80 hours or 210 hours, the time until sintering is completed becomes long, and pores are formed. It is presumed that sufficient time could be taken for the air to be expelled, and therefore the porosity could be lowered. The ferrite sintered body corresponding to the conventional product having a porosity of 2.5% or more was obtained by raising the temperature from 600° C. to 1200° C. at a rate of 4° C./min.

The control of the porosity by the firing profile is merely an example, and the same effect can be obtained by setting the desired porosity by another method. Therefore, the ferrite core 20 having a porosity of 1.00% or less in the winding core portion 30 may be realized by a method other than employing the firing profile described above.

The ferrite sintered body constituting the ferrite core 20 having a porosity of 1.00% or less in the core portion 30 exhibited a high density of 5.2 g/cm ³ or more and 5.4 g/cm ³ or less. . Thus, by setting the density to 5.2 g/cm ³ or more and 5.4 g/cm ³ or less, the effect of reducing the porosity to 1.00% or less is dramatically exhibited. It can be obtained using the Archimedes method.

Referring to FIG. 2, the length dimension L of the ferrite core, that is, the ferrite sintered body 20 measured in the length direction Ld is preferably 0.2 mm or more and 6.0 mm or less. The ferrite core 20 having such relatively small dimensions tends to have low mechanical strength, and therefore it is significant to reduce the porosity to improve the mechanical strength.

Regarding the dimension measured in the width direction Wd of the ferrite sintered body 20, the dimension w of the core portion 30 is preferably 0.3 times or more and 0.6 times or less the dimension W of the flange portion 40. Similarly, regarding the dimension measured in the height direction Td of the ferrite sintered body 20, the dimension t of the core portion 30 is preferably 0.3 times or more and 0.6 times or less the dimension T of the flange portion 40. be. If such a dimensional relationship is selected, the steps in the height direction Ld and the width direction Wd between the winding core portion 30 and the flange portion 40 can be increased. It is possible to secure a large area for arrangement.

[Second embodiment]
Referring to FIG. 6, ferrite core 21 has a vertically asymmetric shape, and winding core portion 30 of ferrite core 21 is provided at a position shifted from center C1 of flange portion 40 in height direction Td. More specifically, the center C2 of the core portion 30 in the height direction Td is provided at a position shifted upward from the center C1 of the flange portion 40 in the height direction Td. A deviation amount B between the center C2 of the winding core portion 30 and the center C1 of the flange portion 40 can be, for example, about 0.01 to 0.025 mm.

According to this embodiment, the terminal electrode 50 (see FIG. 1) is formed on the bottom surface 46 of the collar portion 40 . That is, the terminal electrode 50 is formed on the lower surface 46 located on the side opposite to the side where the winding core portion 30 is biased with respect to the center C1. Therefore, the separation distance between the core portion 30 and the terminal electrode 50 can be increased compared to the case where the center C2 of the core portion 30 and the center C1 of the flange portion 40 are aligned. This makes it possible to secure a wide formation area for the terminal electrodes 50 . In addition, the distance between the winding 55 (see FIG. 1) wound around the winding core 30 and the terminal electrode 50 can be widened. Therefore, it is possible to prevent short-circuit failure between the winding 55 wound around the winding core portion 30 and the terminal electrode 50 . Furthermore, for example, when the coil component is mounted on the circuit board, the winding 55 wound around the winding core portion 30 can be kept away from the circuit pattern on the circuit board. As a result, eddy currents are less likely to occur in the circuit pattern due to the windings 55 of the coil component, and a decrease in the Q value due to an increase in eddy current loss can be suppressed.

In addition, if the ferrite core 21 has a vertically asymmetrical shape, it is difficult to control the pressure during powder press molding, and the winding core 30 is likely to break. .

This ferrite core 21 can be manufactured by a manufacturing method substantially similar to the manufacturing method of the first embodiment.

[Third Embodiment]
Referring to FIG. 7, the winding core portion 30 of the ferrite core 22 has an elliptical or substantially elliptical cross-sectional shape orthogonal to the length direction Ld, and the major axis direction of the cross section faces the width direction Wd. and ribs 36 protruding outward from both ends of the body portion 35 in the width direction Wd. Ribs 36 are provided to prevent damage to the punch during the manufacturing process.

In the ferrite core 22, the cross section of the winding core portion 30 perpendicular to the length direction Ld is formed in an elliptical or substantially elliptical shape. , the wire breakage of the winding 55 can be made less likely to occur when the winding 55 is wound.

If the cross section of the winding core 30 is a simple circle, it is very difficult to obtain this by powder press molding. However, if the ribs 36 are provided on the core portion 30 as in this embodiment, it becomes easier to reduce the porosity.

In this embodiment, the ratio t/T of the maximum dimension t along the height direction Td of the core portion 30 to the height dimension T of the collar portion 40 is 0.3≦t/T≦0.6. Also, the ratio w/W of the maximum dimension w along the width direction Wd of the winding core portion 30 to the width dimension W of the collar portion 40 is 0.3≤w/W≤0.6. is preferred.

This ferrite core 22 can be manufactured by a manufacturing method substantially similar to the manufacturing method of the first embodiment.

Although the present invention has been described in relation to the illustrated embodiments, various other embodiments are possible within the scope of the present invention.

For example, the above-described embodiments relate to a ferrite core provided in a coil component having a single wire, but for example, a coil component that configures a common mode choke coil or a coil component that configures a transformer may include a plurality of wires. The present invention can also be applied to a ferrite core provided in a coil component having a wire of . The present invention can also be applied to ferrite cores provided in wire-wound electronic components (for example, antennas) other than coil components.

Moreover, when configuring a coil component, a plate-like core may be further provided for connecting between a pair of flange portions provided on the ferrite core. According to this configuration, a closed magnetic circuit in which the magnetic flux circulates can be configured. Also, a resin coating may be applied to connect the upper surfaces of the pair of flanges.

Further, the illustrated ferrite core is applied to a horizontal winding type coil component, but the present invention can also be applied to a ferrite core applied to a vertical winding type coil component.

The present invention also extends to partial permutations and combinations of configurations between the different embodiments described above.

10 coil component 20, 21, 22 ferrite core (ferrite sintered body)
30 winding core 40 flange

Claims (12)

A winding core extending in the length direction and flanges provided at both ends of the winding core in the length direction and protruding from the winding core in a height direction orthogonal to the length direction are integrally formed. It consists of a ferrite sintered body itself , which is a sintered body of a pressure-molded body of ferrite powder formed in
Regarding the dimension measured in the height direction, the dimension of the winding core is 0.3 times or more and 0.6 times or less than the dimension of the collar,
Pores are present inside the winding core portion and the flange portion,
The existence ratio of the pores in the winding core is 0.05% or more and 1.00% or less,
The existence ratio of the pores in the collar is 0.05% or more and 1.20% or less,
Ferrite core. 2. The ferrite core according to claim 1, wherein the existence ratio of said pores in said winding core is 0.70% or less. 3. The ferrite core according to claim 2, wherein the existence ratio of said pores in said winding core is 0.50% or less. 4. The ferrite core according to any one of claims 1 to 3, wherein the existence ratio of said pores in said flange is 0.84% or less. 5. The ferrite core according to claim 4, wherein the existence ratio of said pores in said flange is 0.60% or less. The ferrite core according to any one of claims 1 to 5, wherein the ferrite sintered body has a density of 5.2 g/ ^cm3 or more and 5.4 g/ ^cm3 or less. 7. The flange according to any one of claims 1 to 6, wherein the flange protrudes from the winding core not only in the height direction but also in the width direction orthogonal to both the length direction and the height direction. ferrite core. 8. Regarding both the dimension measured in the height direction and the dimension measured in the width direction, the dimension of the core portion is 0.3 times or more and 0.6 times or less than the dimension of the flange portion. The ferrite core described in . 9. The ferrite core according to claim 1, wherein said ferrite sintered body has a dimension measured in said length direction of 0.2 mm or more and 6.0 mm or less. 10. The ferrite core according to claim 1, further comprising a terminal electrode formed on one side of said flange in said height direction. a ferrite core according to claim 10;
a winding arranged on the winding core;
with
Both ends of the winding are electrically connected to the terminal electrodes,
Wound coil parts. 12. The wound coil component according to claim 11, further comprising a plate-shaped core arranged on the other side of the flange in the height direction.

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